In recent years, in the field of microfabrication in the manufacture of semiconductor devices and liquid crystal devices, a finer fabrication technique is rapidly advancing due to the progress of a lithography technology. Typically, shorter wavelength of irradiation light has been used as the finer fabrication technique. Specifically, the irradiation light has been changed from conventional ultraviolet rays typified by the g-line (wavelength: 438 nm) and the i-line (wavelength: 365 nm) to DUV (Deep Ultra Violet) rays.
Presently, KrF excimer laser (wavelength: 248 nm) lithography technology has been introduced into the market, and ArF excimer laser (wavelength: 193 nm) lithography technology, which is directed toward a laser with a shorter wavelength, is being introduced. Moreover, F2 excimer laser (wavelength: 157 nm) lithography technology is studied as a next generation technology. Furthermore, electron beams lithography technology and EUV lithography technology using an extreme ultra violet light (EUV light) around a wavelength of 13.5 nm are also intensively studied as lithography technologies somewhat different from the technologies.
As a resist with high resolution for such an irradiation light with a short wavelength or electron beams, a “chemically amplified resist” containing a photo acid generator has been proposed, and at present, improvement and development of a chemically amplified resist have vigorously been progressing.
As a resist resin used in ArF excimer laser lithography, an acryl resin that is transparent to a light with a wavelength of 193 nm has received attention. As such an acrylic resin, Patent Document 1 discloses a chemically amplified resist composition containing a polymer which exhibits alkali solubility by the decomposition of a side chain thereof.
However, when such a polymer is used as a resist composition for ArF excimer laser lithography, there is a problem in the solubility thereof in a developer. The problem causes defects and large line edge roughness.
On the other hand, in KrF excimer laser lithography, Patent Document 2 describes a resist composition having high resolution and excellent etching resistance. In this document, a hydroxyistyrene resin prepared by copolymerizing a crosslinking agent having an acid-decomposing tertiary ester structure is used as a raw material.
However, since the resin described in Patent Document 2 is a styrene resin, it cannot be used for ArF excimer laser lithography. An acrylic resin prepared by copolymerizing the crosslinking agent having a tertiary ester structure as described in Patent Document 2 may be used. However, line edge roughness or defects cannot sufficiently be improved even if the crosslinking agent having an acid-decomposing tertiary ester structure is simply copolymerized with an acrylic resin.
Patent Document 1: Japanese Patent Laid-Open No. 2003-122007
Patent Document 2: Japanese Patent Laid-Open No. 2002-62656